The present invention is directed to dispensing devices for discharging predetermined quantities of viscous or semi-viscous materials from the nozzle of a gun-like device having a manually actuated trigger structure for selectively discharging the materials from the gun. In particular, the discharge device of the present invention is primarily adapted for the application of relatively small quantities of viscous or semi-viscous liquid insecticides or pesticides to be applied to relatively small target areas in accurate and repeatable sequences.
The following United States patents represent typical prior art dispensing devices for discharging liquid materials, including viscous or semi-viscous materials: U.S. Pat. Nos. 3,141,583; 3,517,688; 3,545,680; 4,062,480; 4,083,474; 4,394,945; 4,531,912; 4,678,107; 4,809,885; 4,821,927; 4,923,096; 4,991,747; 5,022,563; 5,064,098; 5,065,910; and 5,137,187.
It is an object of the present invention to overcome disadvantages of the known prior art dispensing guns. In particular, the discharge devices encompassed within the scope of the present invention provide manually actuated dispensing guns including means for presetting selected quantities of material to be discharged from the device, and assuring that the precisely metered quantity of discharged material are applied in repeatable sequences at the selection of the user. The dispensing gun is adapted to operate as a vacuum driven system, and includes suction generating means for evacuating a discharge chamber to prevent dripping of material from the gun after the desired quantity of material has been discharged. The dispensing gun is particularly adapted to the discharge and application of viscous and semi-viscous materials, and in particular, liquid pesticides and insecticides, which, by the nature of the products, precisely measured, relatively small quantities of material are discharged and applied to well defined and closely confined target locations. It is the further object of the present invention to provide a dispensing device including means for adjusting one or more of the preset quantities of material dischargeable from the gun, and further providing means for readily enabling the user to discharge the same predetermined quantities of material from the gun in easily repeatable selected sequences.
Other objects and advantages of the present invention will become apparent from the following discussion in conjunction with the accompanying drawings.